Oil wells are generally formed by drilling a bore into the earth for accessing buried crude oil deposits, and then installing a variety of equipment within the bore to enable pumping of crude oil up to the earth's surface. During drilling, hollow metallic tubes (also known as “casings”) are inserted within the bore to prevent walls of bore from collapsing. In a deep enough bore, multiple hollow casings are installed vertically one above the other by screwing ends of adjacent sections with each other. The entire assembly of attached casings is commonly known as “bore casing.”
Once a bore casing is formed, a variety of equipment (including crude oil pumping equipment and sensor equipment) is installed within the bore casing. In an operational oil well, crude oil is pumped to the surface of the earth from the buried crude oil deposits with the help of pumping equipment installed in the bore casing.
However, the process of drilling an oil well-bore, installing equipment in it and even operating an existing well-bore are vulnerable to a variety of problems. For example, during drilling, the drilling equipment may fail to perform due to a snag or the coiled tubing (or drill string) may simply get stuck in the bore due to changed earth conditions within the bore. Additionally, with advanced recovery techniques, after being drilled vertically to a certain depth, the bore is often turned and extended on a horizontal route within the earth. Drilling a vertical to horizontal route is challenging and is more vulnerable to both sticking and to failure of equipment. Thus, the drill string often includes a jar, which is a device providing linear hammer impacts during drilling, to help free the stuck drill string or stuck equipment. See e.g. U.S. Pat. No. 8,151,910 (incorporated by reference).
Coiled tubing can be used for directional drilling as well as equipment recover. In one application of coiled tubing in directional drilling, a mud motor is used to create a system for drilling reservoirs. Bottom hole assemblies (BHAs) are now able to drill directional, S-curve and horizontal wells and can be the key to unlocking reserves in mature oilfields via re-entry drilling. Coiled tubing drilling is known for its speed and ability to drill reservoirs in an underbalanced condition and for directional applications, and for its ability to reduce drilling times between 30%-60% compared with conventional jointed pipe drilling rigs. Therefore, its use in directional drilling can provide significant economic benefits.
Coiled tubing rides out on a powered drum during drilling or equipment recovery operations. In addition to a jar, the coiled tubing drill string may include an oscillating tool. See e.g. US Publ'n No. 20150211317 (incorporated by reference). While the impact hammer of a jar provides linear hammering impacts, the oscillating tool provides vibrational impacts to assist in opening a path for the drill string during drilling, or freeing of target equipment during recovery. Nevertheless, if a portion of coiled tubing (which is generally flexible) connects the jar (including an impact hammer) and the oscillating tool, some of the generated impacts get dampened. This can reduce the intended effect of these tools.
Though some currently known coiled tubing tool assemblies claim to facilitate drilling and liberation of target equipment, the damping noted above takes place and negatively affects effectiveness of generated linear/vibrational impacts. Additionally, improperly controlled generation of linear/vibrational impacts can result in impacts either be too weak for efficient drilling or so large as to cause excessive caving-in around the drill string. This effect may be exacerbated while turning a drill string (to drill horizontally or otherwise) through shale (which is softer than bedrock). More specifically, adjusting the frequency and amplitude of vibrational impacts generated by the oscillating tool can significantly enhance directional drilling. Also, in a recovery operation, if the frequency and amplitude of vibrational impacts is too large, it may cause disturbances on surroundings and can even damage the target equipment.
Hence, additional and improved means for adjustment and tuning of the vibrational impacts is a desirable feature of tools for directional drilling or recovery operations.